The present invention relates generally to methods of compressing waveforms of musical tones, voices and various other sounds by use of a vector quantization technique. More particularly, the present invention relates to an improved waveform compression method which can efficiently compress waveform data, e.g., in a situation where a great number of sets of waveform data are prestored in memory in corresponding relation to a variety of rendition styles (performance styles), as well as to a waveform generation method of using such an improved waveform compression method to generate a desired waveform.
The present invention also relates to a waveform generation method of generating a desired waveform using the improved waveform compression method, which is characterized by improved compression of a non-harmonic (i.e., non-periodic) wave components. The present invention relates further to an improvement method that is directed to generating a desired waveform of a non-periodic wave component.
The principles of present invention described hereinbelow can be applied so extensively to apparatus and methods in all fields which have functions of generating musical tones, voices and other sounds, such as automatic performance apparatus, computers, electronic game apparatus and other multimedia equipment, to say nothing of electronic musical instruments. Note that the terms xe2x80x9ctone waveformxe2x80x9d are used in this patent specification to refer to not only to a waveform of a musical tone but also a waveform of a voice or any other sound.
In the electronic tone synthesis techniques known today, the issue of how to synthesize high-quality tones taking into consideration (or reflecting) different rendition styles is getting more and more important. Namely, in the field of natural musical instruments, it has been known that even a tone of a same instrument tone color and same pitch is generated with different tonal characteristics (particularly, different tone color waveforms) in response to performance in different rendition styles, such as a vibrato rendition style and slur rendition style. When such high-quality tones reflecting differences in the rendition styles are to be generated by an electronic musical instrument or the like using an electronic tone synthesis technique, one possible approach is to prestore into memory, for each tone pitch (or range) of each instrument tone color, different sets of waveform data presenting tonal characteristics (especially, tone color waveforms) corresponding to the different rendition styles in association with the rendition styles. In this approach, a tone waveform presenting unique tonal characteristics (especially, a unique tone color waveform) corresponding to a selected rendition style can be generated by reading out one of the waveform data sets which corresponds to the selected rendition style.
In the case where different sets of waveform data are prestored, for each tone pitch (or range) of each instrument tone color, in association with a plurality of rendition styles as mentioned above, the necessary memory storage capacity has to be increased considerably if the waveform data are prestored in an ordinary manner. Thus, how to compress the waveform data efficiently and thereby save the memory storage capacity would become an important challenge. For this reason, some of the conventionally-known waveform data compression techniques which are considered most noteworthy in connection with the present invention will be discussed below.
First, Japanese Patent Laid-open Publication No. SHO-61-104400 discloses a sound recording method, in accordance with which an input waveform is separated, via a filtering process, into a periodic wave component and a non-periodic wave component and the thus-separated periodic and non-periodic wave components are encoded by use of different data-compressing coding schemes and then individually stored into a waveform memory. Although this No. HEI-61-104400 publication teaches the idea of separating specific waveform data into periodic and non-periodic wave components and storing them in compressed data formats, it does not teach the idea of vector-quantizing all of the wave components. For the non-periodic wave component, in particular, the disclosed technique can merely record a residual waveform, obtained by subtracting a waveform of the periodic wave component from the specific waveform data, in a time-serial manner just as it is.
Further, in Japanese Patent Laid-open Publication No. HEI-5-88911, there is disclosed a sound coding method using vector quantization. According to the disclosure, a sound waveform to be compressed is first processed by a filter with characteristics opposite to a spectrum extracted from the sound waveform, and then vector quantization is performed on the periodic wave component of the thus-filtered sound waveform using an excitation vector extracted from a predetermined previous cycle of the sound waveform and also-on the non-periodic wave component of the sound waveform using a noise vector. In the disclosed method, the noise vector is one provided in advance merely as a fixed vector, and the non-periodic wave component is not extracted directly from the sound waveform for the vector quantization based on the noise vector.
However, because the data compression rate is relatively low in the first-mentioned waveform data compression technique (Japanese Patent Laid-open Publication No. SHO-61-104400), it is difficult to achieve sufficient data compression that suits the purpose of storing, for each tone pitch (or range) of each instrument tone color, different sets of waveform data in association with a plurality of rendition styles. Namely, because the above-mentioned waveform data compression technique completely lacks the idea of vector-quantizing the non-periodic wave component, it can do nothing, about data storage of the non-periodic wave component, more than just recording the residual waveform (obtained by subtracting the waveform of the periodic wave component from the sound waveform) in a time series just as it is, and therefore the conventional waveform data compression technique never achieves sufficient data compression.
Further, because the second-mentioned waveform data compression technique (Japanese Patent Laid-open Publication No. HEI-5-88911) uses, as the noise vector, one previously provided as a fixed vector and, besides, is not arranged to extract the non-periodic wave component (noise component) directly from the sound waveform for the subsequent vector quantization, the vector quantization using the noise vector would be performed with poor accuracy, and the non-periodic wave component can never be compressed efficiently and also can never be reproduced with good accuracy. Further, because the filtering process is always performed using the opposite characteristics, the waveform to be reproduced would unavoidably assume a shape substantially different from the original waveform shape due to the intervention of the filtering process of the strong opposite characteristics, which would result in even poorer waveform reproducibility. Therefore, this conventional waveform data compression technique can not be used suitably for waveform reproduction of a musical instrument tone of which highly accurate waveform reproducibility is normally required, although it may be suitable for use in waveform reproduction of a human voice of which very accurate waveform reproducibility is not required. Furthermore, in this conventional waveform data compression technique, which performs the waveform compression using both the periodic vector and the noise vector, there would arise a need to perform the vector quantization, based on a combination of the periodic and noise vectors, on a single waveform having undergone the opposite-characteristic filtering process, which thus presents the problems that such a combination of the periodic and noise vectors can not be determined easily and the waveform data can not be compressed with sufficient accuracy. In addition, because the above-mentioned periodic vector is an excitation vector extracted from a previous waveform in most cases, the conventional technique would present poor followability with respect to a waveform rich in variations.
It is therefore an object of the present invention to provide a waveform compression method which achieves a superior data compressing efficiency and superior reproducibility of an original waveform. It is another object of the present invention to provide a waveform generation method of generating a desired waveform using such a waveform compression method.
Further, it is an object of the present invention to provide a waveform compression method which can effectively and efficiently compress a waveform, especially, a waveform of a non-harmonic wave component (non-periodic wave component). It is another object of the present invention to provide a waveform generation method of generating a desired waveform, especially, a desired waveform of a non-harmonic wave component, using such a waveform compression method.
According one aspect of the present invention, there is provided a waveform compression method, which comprises: a step of separating input waveform data into a harmonic wave component and a non-harmonic wave component; a step of providing a harmonic vector; a step of generating first compressed data by vector-quantizing the separated harmonic wave component using the harmonic vector; a step of providing a non-harmonic vector; and a step of generating second compressed data by vector-quantizing the separated non-harmonic wave component using the non-harmonic vector.
The present invention is characterized primarily in that input waveform data are separated into a harmonic (i.e., periodic) wave component and a non-harmonic (i.e., non-periodic) wave component and these harmonic wave component and non-harmonic wave component are individually subjected to a vector quantization process. Thus vector-quantizing both the harmonic wave component and the non-harmonic wave component according to the present invention can significantly enhance a waveform compressing efficiency. Further, the present invention can perform the vector quantization without the need for taking into account a hard-to-determine combination of a periodic vector and noise vector as in the conventionally-known techniques and is arranged to select respective vectors of the harmonic and non-harmonic wave components independently of each other, so that the present invention can perform the vector quantization process with greater facility. In addition, because the vector quantization of the non-periodic wave component is performed on the basis of the non-harmonic wave component separated or directly extracted from the original waveform, the non-periodic wave component can be reproduced with greatly increased accuracy. As a result, the present invention can significantly facilitate selection of vectors and achieve a superior compressing efficiency in the vector quantization process and superior reproducibility of the original waveform.
As an example, the harmonic wave component may be obtained by performing a frequency analysis of the input waveform data through the fast Fourier transform to extract its fundamental pitch frequency component and harmonic components out of the input waveform data. Namely, a waveform of the harmonic (periodic) wave component can be generated by performing the inverse Fourier transform using the thus-extracted fundamental pitch frequency component and harmonic components; note that the term xe2x80x9charmonic componentsxe2x80x9d is used herein distinctly from the term xe2x80x9charmonic wave componentxe2x80x9d. Then, a waveform of the non-harmonic wave component can be provided as a residual waveform that is derived from subtracting the waveform of the harmonic wave component from the input waveform data.
Because the harmonic wave component, in principle, can be regarded as a repetitive waveform, the harmonic wave component can be reproduced such as by using and looping a particular single- or plural-cycle waveform as a representative vector (or looping two successive representative vectors in a cross-fading fashion). Therefore, Each such representative vector can be used as a harmonic vector in the present invention. For example, the vector quantization of the harmonic wave component, separated from the input waveform data, can be performed by selecting a harmonic vector , i.e., a representative vector, and adding thereto information describing how the selected harmonic vector, i.e., representative vector, is to be used (e.g., a section where the vector is to be used, a manner in which the vector is to be looped, an amplitude envelope to be imparted to the vector, and the like).
On the other hand, it is preferable that the non-harmonic wave component be subjected to optimal vector quantization appropriate to characteristics or contents of the non-harmonic wave component in question, taking into account trade-off between promotion of data compression and waveform reproducibility. Although the non-harmonic wave component corresponds basically to a non-repetitive, random noise waveform, a waveform of a non-harmonic wave component of a necessary time length may be reproduced by performing a looping operation on a given representative vector taking into consideration a degree of importance as to its contents and position within a sounding period (this form of reproduction is called xe2x80x9cloop reproductionxe2x80x9d), or by using a representative vector of a necessary time length only once with no looping (this form of reproduction is called xe2x80x9cone-shot reproductionxe2x80x9d). In an alternative, a waveform of a given non-harmonic wave component may be reproduced by combining two or more representative vectors while switching between different combinations of the vectors in a predetermined order (this form of reproduction is called xe2x80x9csequence reproductionxe2x80x9d), or the order or sequence to switch between the combinations may be set randomly so as to emphasize noise or random characteristics of the non-harmonic wave component (this form of reproduction is called xe2x80x9crandom sequence reproductionxe2x80x9d). As mentioned above, it is preferable to use, as non-harmonic vectors, representative vectors appropriate to various optimal forms of the vector quantization. Thus, the vector quantization may be performed on the non-harmonic wave component, separated from the input waveform data, such as by selecting a non-harmonic vector, i.e., a representative vector, suitable for the non-harmonic wave component in question and adding thereto information describing how the selected harmonic vector, i.e., representative vector, is to be used (e.g., a section and/or period to which the loop reproduction, one-shot reproduction or the like is to be applied, form of an amplitude envelope to be imparted to the vector, and the like).
Each of the representative vectors or harmonic vectors of the harmonic wave components and each of the representative vectors or non-harmonic vectors of the harmonic wave components can be shaped between various different waveforms. Namely, as long as two or more different original waveforms to be compressed have a predetermined commonality in certain of their segments, then a same representative vector can be shared between the different original waveforms, as necessary, at the time of the vector quantization.
According to another aspect of the present invention, there is provided a waveform generation method, which comprises: a step of receiving first compressed data including vector information indicative of a harmonic vector and second compressed data including vector information indicative of a non-harmonic vector; a step of providing a harmonic vector; a step of synthesizing waveform data of a harmonic wave component on the basis of the first compressed data and the harmonic vector indicated thereby; a step of providing a non-harmonic vector; and a step of synthesizing waveform data of a non-harmonic wave component on the basis of the second compressed data and the non-harmonic vector indicated thereby.
With the above-mentioned arrangements, the waveform generation method can reproduce waveforms of harmonic and non-harmonic wave components, independently of each other, from the compressed data of the harmonic wave component (first compressed data) and compressed data of the non-harmonic wave component (second compressed data). Then, the original waveform can be reproduced by combining together the thus-reproduced waveforms of the harmonic and non-harmonic wave components.
According to still another aspect of the present invention, there is provided a waveform compression method, which comprises: a step of providing separately a harmonic wave component and a non-harmonic wave component of waveform data to be compressed; a step of detecting periodicity of the provided harmonic wave component; a step of dividing the non-harmonic wave component into a plurality of sections on the basis of the detected periodicity of the harmonic wave component; a step of providing a non-harmonic vector; and a step of generating compressed data of a non-harmonic wave component by vector-quantizing a non-harmonic wave component of each of the sections using the provided non-harmonic vector.
Waveform data to be compressed are separated, by means of an appropriate technique, into a harmonic wave component and a non-harmonic wave component and provided separately. According to the present invention, a vector quantization process is performed at least on the non-harmonic wave component. To vector-quantize a waveform of the non-harmonic wave component, it is desirable that the waveform of the non-harmonic wave component (i.e., non-harmonic component waveform) be divided into a plurality of sections and optimal vector quantization be performed for each of the thus-divided sections. As a preferred technique of dividing the non-harmonic component waveform into a plurality of sections, the present invention is arranged to detect periodicity of the harmonic wave component corresponding to the non-harmonic wave component and divide the non-harmonic wave component into a plurality of sections on the basis of the detected periodicity of the harmonic wave component. For example, the non-harmonic component waveform may be divided into a plurality of sections over a time period corresponding to an integral multiple or fractional multiple of a period (or cycle) of the harmonic wave component. It should be obvious that the divided sections need not necessarily be at equal intervals and may have different lengths as appropriate; for example, one of the divided sections may have a length corresponding to half the cycle of the harmonic wave component, another one of the divided sections may have a length corresponding to eight cycles of the harmonic wave component, and so on.
Such a technique of dividing the non-harmonic component waveform on the basis of the detected periodicity of the harmonic wave component allows the non-harmonic component waveform to be automatically divided into sections without requiring much human labor and thereby affords a benefit of significantly facilitating the analyzing operations. Further, in a situation where the character of the non-harmonic component waveform depends more or less on the periodicity of the harmonic wave component, the dividing technique allows an appropriate waveform division to be performed with great facility. Further, because the vector quantization of the non-periodic wave component is performed on the basis of the peculiar non-harmonic wave component constituting the original waveform in conjunction with the harmonic wave component, the present invention can reproduce the non-periodic wave component with significantly increased accuracy or reproducibility.
Specifically, when a waveform of a periodic or harmonic wave component (periodic or harmonic component waveform) is to be vector-quantized, a representative vector (a representative waveform segment) is selected ordinarily in such a section where similarity in the waveform shape is found. Thus, when vector-quantizing a non-periodic wave component (non-harmonic wave component) as well, it becomes important to perform an appropriate waveform division by judging in which of waveform regions or ranges similarity in the waveform shape is found. However, because the non-periodic wave component (non-harmonic wave component) itself presents a noise-like waveform, it is troublesome to identify, visually or otherwise, a particular range of the waveform which shows similarity in the waveform shape and it is also difficult to automatize the processing (i.e., automatically identifying a particular range of the waveform which shows similarity in the waveform shape and automatically dividing the identified range into sections). Therefore, the conventionally-known techniques did not analyze a waveform of a non-periodic wave component (non-harmonic wave component) itself to perform the vector quantization process on the non-periodic wave component independently of the periodic wave component. In contrast, the present invention can highly facilitate analysis of a non-periodic or non-harmonic component waveform itself to thereby allow the vector quantization process to be readily performed on the non-periodic wave component independently of the periodic wave component. Further, with the present invention, the waveform division can be readily automatized, taking advantage of the fact that the periodicity of the periodic or harmonic wave component can be automatically identified with ease. For example, it will be very advantageous to first set a provisional divided section every automatically-identified predetermined cycle of the harmonic wave component and then finally set an appropriate divided section through user""s manual operation (which may include not only appropriately dividing the non-periodic component waveform at locations synchronized with the cycles of the harmonic wave component but also making adjustment to appropriately shift the divided locations forward or backward).
By observing a graphic display of a non-periodic wave component (non-harmonic wave component) separated in accordance with a frequency analysis, it has been newly found that there is some region where the non-periodic wave component appears to be varying in the waveform in cycles similar to those of the corresponding periodic wave component, although the waveform variation can not be separated as a periodic wave component through the frequency analysis. Therefore, dividing the non-periodic component waveform into a plurality of sections, utilizing the periodicity of the harmonic wave component and using appropriate locations synchronized with the cycles of the periodic wave component as waveform-dividing points, should be very useful for appropriately dividing the non-periodic wave component every range having similarity at the time of the vector quantization on the non-harmonic wave component. Thus, the present invention is intended to greatly facilitate the process to compress the non-harmonic wave component, so as to be very useful for realizing vector quantization of the non-harmonic wave component. Further, with such arrangements, the present invention accomplishes various superior benefits; for example, it can highly contribute to an enhanced waveform compressing efficiency and also achieves superior reproducibility of the original waveform and, in particular, the non-harmonic wave component.
Here, it is desirable that the non-harmonic wave component be subjected to optimal vector quantization appropriate to peculiar characteristics or contents of the non-harmonic wave component in question, taking into account trade-off between promotion of data compression and waveform reproducibility. For example, in the vector quantization of the non-harmonic wave component, a representative vector may be selected depending on a particular form or mode of non-harmonic wave component reproduction employed, such as the loop reproduction, one-shot reproduction, sequence reproduction or random sequence reproduction, similarly to the above-mentioned case. Also, each of the representative vector or non-harmonic vector of the non-harmonic wave components can be shared between various different waveforms, as with the above-mentioned case.
According to still another aspect of the present invention, there is provided a waveform generation method, which comprises: a step of receiving compressed data of a non-harmonic wave component including vector information indicative of a non-harmonic vector; a step of providing waveform data of a harmonic wave component to be generated simultaneously; a step of providing a non-harmonic vector; a step of selecting a non-harmonic vector on the basis of the compressed data of the non-harmonic wave component; a step of performing stretch/contraction control of a time-axial length of the selected non-harmonic vector in accordance with periodicity of the waveform data of the harmonic wave component; and a step of synthesizing waveform data of a non-harmonic wave component on the basis of the non-harmonic vector having been subjected to the stretch/contraction control by the step of controlling.
The arrangements allows a non-harmonic vector to be selected on the basis of compressed waveform data of a non-harmonic wave component, so that a waveform of a non-harmonic wave component can be reproduced/generated independently on the basis of the selected non-harmonic vector. At that time, stretch/contraction of the time-axial length of the selected non-harmonic vector is controlled in accordance with periodicity of waveform data of a harmonic wave component to be generated simultaneously, so that waveform data of a non-harmonic wave component are synthesized on the basis of the non-harmonic vector having been subjected to the stretch/contraction control. Such arrangements are advantageously applicable to the case where data compression of a non-harmonic wave component is performed by effecting a waveform division synchronized with periodicity of a corresponding harmonic wave component before vector quantization takes place, as noted earlier. In such a case, because the time-axial length of the non-harmonic vector is related to the periodicity of the corresponding harmonic wave component, appropriately controlling the time-axial length of the non-harmonic vector to stretch or contract in accordance with the periodicity of the harmonic wave component to be reproduced simultaneously will effectively facilitate reproduction of a timewise correspondence between the harmonic component waveform and non-harmonic component waveform of the original waveform, thereby contributing greatly to enhanced reproducibility of the non-harmonic component waveform. In this way, the waveform of the non-harmonic wave component can be reproduced/generated independently from the compressed data of the non-harmonic wave component. Also, mixing the thus-reproduced non-harmonic component waveform with the harmonic component waveform can reproduce the original waveform in an appropriate manner.
According to still another aspect of the present invention, there is provided a waveform compression method, which comprises: a step of providing separately a harmonic wave component and a non-harmonic wave component of waveform data to be compressed; a step of dividing the non-harmonic wave component into a plurality of sections on the basis of a waveform shape of the non-harmonic wave component; a step of providing a non-harmonic vector; and a step of generating compressed data of a non-harmonic wave component by vector-quantizing a non-harmonic wave component of each of the sections using the non-harmonic vector.
Waveform data to be compressed are separated, by means of an appropriate technique, into a harmonic (periodic) wave component and a non-harmonic (non-periodic) wave component and provided separately. According to the present invention, a vector quantization process is performed at least on the non-harmonic wave component. To vector-quantize a non-harmonic component waveform, it is desirable that the non-harmonic component waveform be divided into a plurality of sections and optimal vector quantization be performed for each of the thus-divided sections. As a preferred dividing technique, the present invention is arranged to divide the non-harmonic wave component into a plurality of sections on the basis of a waveform shape of the non-harmonic wave component. In this way, the non-harmonic wave component can be divided at appropriate locations which appear to provide a good data compressing efficiency and do not appear to substantially impair waveform reproducibility judging from the waveform shape of the non-harmonic wave component in question.
As with the above-discussed cases, it is preferable that the non-harmonic wave component be subjected to optimal vector quantization appropriate to characteristics or contents of the non-harmonic wave component in question, taking into account trade-off between promotion of data compression and waveform reproducibility. Although the non-harmonic wave component corresponds basically to a non-repetitive, random noise waveform, using a section division scheme considered optimal in view of its waveform shape and performing vector quantization based thereon will achieve efficient data compression and allow subsequent waveform generation processing to be performed with efficiency. For instance, for the above-mentioned xe2x80x9cloop reproductionxe2x80x9d, a non-harmonic component waveform of a necessary time length may be reproduced by performing the vector quantization in such a manner to loop a specific representative vector, taking into consideration a degree of importance as to its shape and position within a predetermined sounding period, and then performing a loop reproduction process at the time of reproduction. Further, for the above-mentioned xe2x80x9cone-shot reproductionxe2x80x9d, a given non-harmonic component waveform may be reproduced by performing the vector quantization in such a manner to use a representative vector of a necessary time length only once with no looping and then performing a reproduction process based thereon at the time of reproduction. In addition, as in the above-mentioned cases, a representative vector may be selected depending on a particular form or mode of non-harmonic wave component reproduction employed, such as the sequence reproduction or random sequence reproduction. Also, each of the representative vectors or non-harmonic vectors of the non-harmonic wave components can be shared between various different waveforms.
Namely, the present invention can highly facilitate analysis of a non-periodic component (non-harmonic wave component) waveform itself and vector quantization process on the non-periodic wave component independent of analysis of the periodic wave component which could not be readily conducted in the past. Further, because the vector quantization of the non-periodic wave component is performed on the basis of the peculiar non-harmonic wave component constituting the original waveform in conjunction with the harmonic wave component, the present invention can reproduce the non-periodic wave component with greatly increased accuracy or reproducibility. Thus, the present invention is intended to greatly facilitate the process to compress the non-harmonic wave component, so as to be very useful for realizing the vector quantization of the non-harmonic wave component. Further, with such arrangements, the present invention accomplishes various superior benefits; for example, it can highly contribute to an enhanced waveform compressing efficiency and also achieves superior reproducibility of the original waveform and, in particular, the non-harmonic wave component.
According to still another aspect of the present invention, there is provided a waveform generation method, which comprises: a step of providing waveform data of a harmonic wave component; a step of providing compressed data of non-harmonic wave components, respectively, for a plurality of sections, a step of providing a non-harmonic vector; and a step of selecting a non-harmonic vector on the basis of the compressed data of the non-harmonic wave component for each of the sections and generating waveform data of a non-harmonic wave component for each of the sections on the basis of the selected non-harmonic vector. In this waveform generation method, a waveform is generated by combining the waveform data of the harmonic wave component and the waveform data of the non-harmonic wave component. The waveform data for a given one of the sections include information indicating that no non-harmonic vector is to be used for the given section, so that waveform data of a harmonic wave component are generated for the given section without a non-harmonic wave component.
With the arrangements, the present invention can safely ignore a non-harmonic wave component present in such a section that is not so important in characterizing a sound, and thus can construct a reproduced waveform using only the harmonic wave component with the non-harmonic wave component muted or silenced for that section. Accordingly, it is possible to enhance the data compressing efficiency of the non-harmonic wave component.
According to still another aspect of the present invention, there is provided a waveform generation method, which comprises: a step of providing waveform data of a harmonic wave component; a step of providing compressed data of non-harmonic wave components, respectively, for a plurality of sections, a step of providing a non-harmonic vector; and a step of selecting a non-harmonic vector on the basis of the compressed data of the non-harmonic wave component for each of the sections and generating waveform data of a non-harmonic wave component for each of the sections on the basis of the selected non-harmonic vector. In this method, a waveform is generated by combining the waveform data of the harmonic wave component and the waveform data of the non-harmonic wave component. The waveform data for a given one of the sections include information indicating that the non-harmonic vector is to be used repetitively for the given section, so that waveform data of a harmonic wave component are generated for the given section by repeating the non-harmonic vector.
With the arrangements, the present invention reproduces, in a looping fashion, a non-harmonic wave component present in such a section that is not important in characterizing a sound, and accordingly, it is possible to enhance the data compressing efficiency of the non-harmonic wave component. For example, for a section having a relatively great sound volume in an original waveform, which is subject to a great influence of a harmonic component waveform, highly elaborate reproducibility is not required of a non-harmonic wave component and a waveform of the non-harmonic wave component can be reproduced/generated, without involving any significant problems, by just looping a non-harmonic vector of a limited data size. The inventive waveform generation method can be applied very advantageously to such a situation.
According to still another aspect of the present invention, there is provided a waveform generation method, which comprises: a step of providing waveform data of a harmonic wave component in correspondence with a rendition style designated from among a plurality of different rendition styles; a step of providing compressed data of a non-harmonic wave component in correspondence with the designated rendition style; a step of providing non-harmonic vectors via a memory storing a plurality of non-harmonic vectors; and a step of, on the basis of the compressed data of the non-harmonic wave component, selecting a non-harmonic vector from among the plurality of non-harmonic vectors provided via the memory and generating waveform data of a non-harmonic wave component on the basis of the selected non-harmonic vector. In the inventive tone generation method, a waveform corresponding to the designated rendition style is generated by combining the waveform data of the harmonic wave component and the waveform data of the non-harmonic wave component.
With the arrangements, the waveform of the non-harmonic wave component can be reproduced/generated independently from the compressed data of the harmonic wave component. Also, mixing the thus-reproduced non-harmonic component waveform with the harmonic component waveform can reproduce a unique original waveform corresponding to the designated rendition style.
The present invention may be constructed and implemented not only as a method invention as discussed above but also as an apparatus invention. Further, the present invention may be arranged and implemented as a program for causing a computer, microprocessor or the like to execute the inventive method, as well as a machine-readable storage medium storing such a program. Furthermore, the present invention may be implemented as a storage medium containing waveform data in a novel compressed data format. In addition, the hardware for use in implementing the present invention may comprise a functionally-fixed hardware device including a combination of discrete circuits, such as logic circuitry and gate array or an integrated circuit, without being necessarily limited to a programmable facility such as a computer or microprocessor. Stated differently, the processor in the inventive apparatus may be a non-programable processor or control unit only having a fixed processing function, not to mention a programmable processor such as a computer or microprocessor. Further, the electronic musical instrument embodying the present invention may be of any other type than the keyboard-based type. Furthermore, the waveform generation apparatus or music performance apparatus of the present invention may be a personal computer so programmed as to be capable of music performance, rather than being constructed as an electronic musical instrument. Moreover, the waveform generation apparatus or music performance apparatus of the present invention may be a karaoke apparatus, game apparatus, cellular (mobile) phone or any other type of multimedia equipment.